Display units for providing visual information by applying light from a rear side of a transparent panel with pre-formed symbols are well-known. However, often such displays suffer from a number of disadvantages. It is normally a prerequisite desire of the transparent panels that the information symbols are completely invisible in a deactivated state of the display, i.e. when the light source at the rear side of the display is switched off. Therefore, transparent panels with a semi-transparent rear side or panels made of a semi-transparent material themselves are used as a front of the display so as to give a dark appearance in a deactivated state of the display. Coloured or toned glass or acrylic materials may be used in front of the display to provide this effect.
However, the display region will still be visible to a viewer also in the deactivated state since most often the display will be made of a front material different from the front material of the device to which the display is attached, because often a front panel of a device is a metal panel, thus making it impossible to fully integrate the display unit in the front of the device. The reason for the display panel not being fully integrated with the device front panel is that a transition on the surface between the metal panel of the device and the non-metal panel of the display will always be clearly visible and it will be perceptible if one touches the front surface. If a display panel is attached to a device having a metal front panel the difference in materials will also imply a non-perfect mechanical fit of the display onto or into the front panel of the device. This non-perfect mechanical fit will lead to further disadvantages than non-perfect visual fit as mentioned above. A border edge around the display panel will be inevitable. In addition, attaching a display panel to a front panel of a device will normally involve a penetration of the front panel, such as for electrical wires, thus introducing a path for dust, liquid and gases that may penetrate into the interior of the device thus disturbing the function of the device.
Attempts of producing a display front with an appearance similar to solid metal is known, see for example the earlier application of the applicant WO 03/019505. In this application the formation of a display is described, where translucent regions are created in order to be able to shine light through the metal structure. It thereby becomes possible to display information on the surface of a metal structure where to the user no obvious indications are present that the metal structure serves as a display unit. The document, however, does not describe that the structure may also be used as an input unit, whereby it leaves the serious drawback that for applications, where it is desirable both to display information, but also to receive input, the skilled person will have to provide separate input means, for example in the shape of traditional bottoms, dials, etc. This in turn necessitates that firstly an area of the device where such a structure is built into needs to be larger in order to also accommodate the input means, but also the “pure” design where the surprising effect of having an entire clean metal surface is lost.
In other applications, display fronts which appear to be solid metal have been attempted such as a metal layer being vapour deposited onto a transparent surface thus providing a translucent surface. However, as an example, a glass material must still be used for supporting the metal layer and thereby the visual appearance of an integrated display region and front panel is destroyed. Other attempts to produce displays with metal-like fronts have several layers. Such displays typically have a front sheet of a transparent material positioned in front of a metal sheet thus to a certain degree providing a visual impression of a metal surface.
U.S. Pat. No. 5,987,793 describes a display unit with pre-formed symbols visible from a front side when a light source is applied at a rear side. The display unit has several layers. A transparent sheet forms a front of the display. A 0.01-0.05 μm thick layer of metal, for example aluminium, is applied to the rear side of the transparent sheet. Symbols are formed in a “character cut-out layer” behind the metal layer. The symbols are visible from the front side, when the light source at the rear side is switched on. Without light being switched on at the rear side, only the metal layer is visible from the front side thus giving a visual impression of a metal display. In order to provide a “high-grade feeling” the front side of the transparent panel is coated with a layer of urethane resin.
U.S. Pat. No. 4,417,411 describes a display with a front panel of a transparent material coated with a metal coating with a thickness of 200-300 Å. The metal coating is intended to provide a visual impression of a “metallic wall”, when light at the rear side is switched off.
FR 2 702 296 A3 describes a display with a front sheet being translucent but not transparent. A thickness of 0.1-0.5 mm is considered appropriate for the front sheet, depending on which material is used. The front sheet is positioned in front of a second sheet, for example a metal sheet, the second sheet not being transparent or translucent. Transparent symbols are canted into the second sheet so as to allow symbols to be visible from the front when a light source is applied from the rear side.
JP 2002040952 (English abstract) describes a display with a metal film having a large number of small cavities with a pore diameter of 5-70 μm in a specified pitch by about −20-50% area rate of view area is formed on an upper face side of a transparent substrate. A colour image-forming layer is formed on the upper face side of the metal film, and a transparent protective film layer is formed on the upper face of the colour image-forming layer. An effect being obtained with the described display is a “noble metal appearance”.
JP 2002023670 describes a display with a metallic film in which small cavities having about 40-70 μm diameter are dispersively arranged at prescribed intervals about 20-50% area rate of the surface area is arranged on the lower face of a transparent display substrate.
It is an object of the present invention to provide a metal structure that can serve as a front panel and at the same time allow information to be displayed on a display region of the panel, when a light source is applied on a rear side of the structure. However, the object includes that when the light source is switched off, the display region should not in any way be distinguishable from the remaining part of the panel.